1. Field of the Invention
The present invention relates to an electronic musical instrument and particularly relates to a keyboard electronic musical instrument.
2. Description of the Related Art
A keyboard is most general as means for manipulating the electronic musical instrument. That is, a keyboard is an excellent manipulating means which can be easily operated by a performer and, at the same time, can be easily matched with expression of a feeling. Heretofore, a keyboard electronic musical instrument in which a detection signal corresponding to touch at the time of the depressing of a key in the keyboard is generated to thereby control the strength of the musical tone, is known.
On the other hand, various tone synthesizers having an electric or software model for physically simulating the tone generating mechanism of a natural musical instrument and using the operation of the model have been proposed. If a detection signal generated by the depression of a key is given to this type tone synthesizer, a keyboard electronic musical instrument suitable for musical performance richer in reality can be provided.
To improve representation as a musical instrument, it is necessary that touch at the time of the performer's depressing of a key is faithfully reflected on the resulting tone. FIG. 41 shows a schematic structure (corresponding to one key) related to the detection of key depression in a conventional keyboard electronic musical instrument. As shown in FIG. 41, two switches SW1 and SW2 for detecting key depression are attached to each key KEY supported by a fulcrum in the keyboard. When the key KEY is depressed to a first depth, the switch SW1 is turned on. When the key KEY is depressed to a second depth which is deeper than the first depth, the switch SW2 is turned on.
When the switches SW1 and SW2 are successively turned on by depressing the key KEY, the time difference between the turning-on of the switch SW1 and the turning-on of the switch SW2 is counted by a time difference detecting circuit DET. A key velocity signal corresponding to the key-depressing velocity of the key KEY is generated on the basis of the count result. Then, the strength of the tone to be generated in the tone generator TG is controlled by a central processing unit (CPU) 1 on the basis the key velocity signal.